Mass screening of Southwest United States population for epidemiology and incidence of asymptomatic gallstones. Gallbladder survey is part of Hispanic Health and Nutrition Epidemiologic Survey (HHANES). Soft tissue imaging, harmlessness, and examining speed are attributes of ultrasound scanning that suggest it could become an integral component of health screening. Although gallstones constitute a significan health hazard, little is known about the epidemiology of this disease. In collaboration with the National Center for Health Statistics, gallstone prevalence in Hispanics will be studied. This is the first use of ultrasound as part of a large scale mass epidemiological survey. Study will last 2-3 years and cover approximately 8 states.